Conventionally, when executing a welding operation, to analyze welding phenomena in a micro time region or to measure variations in welding outputs in a macro time region, separately from a welding apparatus or a robot control unit, there is connected a measuring device such as a multipurpose measuring logger or an arc sensor monitor device for collecting and displaying waveform data (For example, see patent literature 1).    Patent literature 1: JP Hei-5-329645 publication